Sound-receiving apparatus



W. L. WALKER.

SOUND RECEIVING APPARATUS. APPLICATION FILED NOV. 19. 1917.

1,41%? 86, Patented May 30), 1922.

New York and entree stares 515.1... it! L. WALKER, NEW YORK, N. Y.

sonnnnnomvrne arrana'rns.

Specification of Letters Patent.

Patented May 3Q 1922..

Application filed November 19, 1917. Serial No. 202,680.

To all whom it may concern:

Be it known that 1, WILLIAM. L. l VALKER, a citizen of the United States of America, and resident of New York, in the county of State of New York, have invented new and useful Improvements in Sound-Receiving Apparatus, of which the following is a specification.

This invention relates to sound signaling and more particularly to submarine signaling and to the detection'of sounds in water. The invention comprises a device which is a more efiicient transmitter of impulses and which consists of a diaphragm of large dimensions. Instead of forming an integral part of the microphone itself of a part of a ships hull the diaphragm forms one side of a sound box and may be balanced by air pressure to compensate for external water pressurewas set forth in my previous applicationsSerial No. 161,179, filed April 11, 1917,. Patent No. 1,349,305, dated Aug. 10, 1920, and Serial No. 176,299, filed June 22, 1917. By this method an exceedingly thin and sensitive diaphragm may be used which will respond to very faint or weak sound waves.

Heretofore in employing microphones in submarine signaling it has been customary to employ so-called solid back micro,

phones, that is, microphones having the back or body portion rigidly mounted on a stationary support. This is unsatisfactory for general submarine signaling, Where it is frequently desirable to faintsounds coming from long distances, for the reason that if the microphone be made sufiiciently sensitive to detect faint sounds it is subject to injury or destruction by heavy sounds produced near the microphone. lit has been. proposed to attach the diaphragm of a microphone to a vibratory sound-receivin device. and to leave the body of the microphone unattached, so that the body can move with the diaphragm when heavy sounds are received and thereby avoid undue displacement of the diaphragm relatively to the body. While this reduces the'danger of injury to the microphone, it also reduces to a large extent the sensitivity of the microphone.

detect very It is the object of the present invention to overcome the aforesaid dificulties and not only to eliminate the danger of injury to the microphone from heavy sounds nearby but also to maintain high sensitivity of the microphones to faint distances. In other words it is the object of this invention-to provide a microphone which is substantially free from the dangers incident to solid-back microphones but which is substantially as sensitive as solidback microphones. y

In one aspect the present-invention comprises a microphone cell having its diaphragm connected to a vibratory sound-receiving device and having its body portion free to move with the diaphragm together with means for yieldingly restraining or damping movement of the body of the microphone. The preferred form of damping means comprises an air vane or baffle plate connected to the microphone body'so that movement of the microphone 'is restrained by the air resistance of the an vane, the an vane being arranged to operate either in the open air or as a piston in a cylinder.

Another phase of the present invention involves pivotally supporting the currentvarylng 'or current-generating device so' be readily actuated by that the device may device with a minimum the sound responslve of frictional resistance and without supporting the current-varying. device upon the sound-responsive device. This method of supporting the current-varying device permits the utilization of a plurality of such devices in cooperative relationsh p with a single sound-responsive device.

The sound-responsive diaphragm is connected to a lever which oscillates in synchronism with the diaphragm. The lever associated with the sound-responsive diaphragm is preferably mounted on a knifeedge support so as practically to eliminate friction and lost motion, the elimination of lost motion being particularly important inasmuch as the amplitude of vibration of the parts may be as low as one-tenth of a millimeter. Attached to this lever is one or more adjustable weights, together with sounds from long -bodiment of the invention,

dragging or damping devices and one or more m1crophon1c cel s,

that is a cell having the electrodes of the microphone of the presbut" witliout the usual external sure type, diaphra These cells are energized 1n the usua manner by a battery and transmit the energ received by currentvariat on to a telep one receiver or other'recording apparatus. I

- Microphones attached to ships are often afiected more y' disturbing noises Set Figure 2 is a side elevation of a modifiedembodiment of the invention,- parts being shown insection;

Figure 3 is aside elevation of another modification of the invention; and

Figure 45 is a side elevation of alever arm carrying" a-plurality of microphones- -The embodiment shown in Fig.1 comprises a sound-responsive device in the form of a diaphra m 1 which may be secured in an opening in the side-of aship or in a sound box, and two currentwarying devices in the form of microphones 2 and 3.- The microphones are supported on a lever 1 which is pivotally mounted, preferably at its central point, one knife-edge support 5. The lever arm 4 is connected to the diaphragm 1 by means which preferably includes a short flexible strip of metal 7 adapted to compensate for the slight-vertical component of movement of the lever arm resulting from its rotary movement about the knife-edge support.

The microphones consist of cells having the electrodes of microphones of the pressure type and the cells are preferably mounted by means of insulators. Thus the microphones 2 and 3 comprise diaphragms 8 and 9 and cup-shaped cells 10 and 11 which contain particles of carbon. The diaphragms 8 and 9 may be held over the openings of the cup-shaped cells in any suitable manner, as for example, by means of the overhanging flanges shown in the drawing. The microphones 2 and 3 are mounted through the medium of their diaphragms byv means of rods 14: and 15, which are preferably of insulating material such as ivory or hard rubber, extending between the lever arm t and ,the central points of the diaplirjagms-.- Weights inthe form-of rods 16 and 17 are preferably threaded or otherwise these disturbances,-

detachably mounted on the carbon cup for the purpose of regulating the weight and inertia of the cup. The rods 16 and 17 rest on bearings 12 and Y13 which support the weight of the rod and microphone cells, the bearings 12 and 13 preferably being disposed inthe region of the center of gravity of the rods and cells taken together so that the rods and microphones are substantially balanced upon the bearings.

The sound responsive diaphragm 1, microphones 2- and 3,-lever 1, ctc., constitute an oscillatory system, the diaphragms 1 supplying the necessary resilience, and I preferably provide some means for regulating tlie period of this vibrating or oscillatory systems Suitable means for this purpose comprises one or more weights 3O adjustably mounted on the lever arm 4. As the weights are moved toward the pivot 5 the efi'ective Weight of the system is reduced and the period is decreased and by moving the weights away from the pivot the inertia of the system is increased and the period is increased.

The embodiment shown in Fig. 2 com prises a sound-responsive device in the form of a diaphragm 18 and microphone cell 20 mounted on the sound-responsive device 18 through the medium ofan insulating connection 22, together with means for regulating the freedom of movement of the body of the microphone cell. This means comprises a cylinder 23 connected with the body of the microphone through the medium of a piston rod 25, the piston, cylinder, microphone and sound-responsive device preferably being disposed colinearly. A number of small holes 21 are provided in the piston or a by-pass 26 is provided around. the piston, or both may be provided, to afford a communication between the'opposite endsof the cylinder, the by-pass 26 preferably being provided with a valve 27 to regulate its effective cross-sectional area. The cylinder 23 may be filled with any suitable fluid which is adapted to retard the movement of the piston longitudinally of the cylinder, the character of the fluid determining the resistance ofi'ered to the movementof the pis-- ton and microphone body. For example, a liquid would afford a greater resistance to the movement of the piston than would a gas. For most purposes air is satisfactory, the density of the air determining the degree of resistance offered to movement of the piston. A-suspension rod 31 containing an insulation section 32 may support the cylinder and hold it in fixed position.

The embodiment shown in Fig. 3 comprises a sound-responsive diaphragm 33, a microphone 34 joined to the sound-responsive diaphragm in a manner similar to that illustrated in Fig. 1, a lever 35 for pivotally be provided to supporting the microphone at least in part, and dampmg or dragging means in the form of a disk 36 mounted on the rear of the microphone cell 37. The lever 35 may be rovirled with an adjustable weight 37 as in ig. 1 and the microphone is preferably insulated from its support by means of an insulating connection 38. The disk 36 prevents a rapid oscillation of the microphone by virtue of the large air resistance which it afi'ords, but at the same time it permits a slow movement of the parts of the 'micro phone when heavy disturbances reach the microphone. To regulate the drag produced by the disk its etl'ective size may-be varied or by varying the size of openings therein or by interchanging disks of difierent sizes. Obviously the disk of Fig. 3 would ofier less resistance to the movement of the carbon cup than would the piston 24 of Fig. 2, especially when the cylinder of Fig. 2 is filled with a liquid. Thus the apparatus of Fig. 2 will respond to lower frequencies than will the apparatus illustrated in Fig. 3, especially when the cylinder is filled with a li uid.

1 ig. a illustrates oneway of associating a relatively large member of microphone cells with a lever arm and at the same time causing them to be afiected equally by vibrations of the oscillating arm so that they may be connected either in parallel or in series. On each end of the lever arm 39 is a cross arm 40 carrying a plurality of microphone cells 41 in a manner similar to that shown in Fig. 1, each of the cells being connected to the lever arm through the medium of its diaphragm and all of the microphones being substantially equidistant from the lever pivot. Any suitable draggingmeans may be associated with the cells as illustrated for example in Figs. -1 to 3 for the purpose of rendering them responsive only to vibrations of particular frequencies. It will be understood that ordinary microphone cells are very light and b Y making the supporting, connecting and dragging parts correspondingly light the system can be vibrated at a relatively high frequency even when carrying a number or 1 icrophone. cells as shown in Fig. l; l

The. operation of the apparatus is as follows: When sound waves impinge on the diaphragm l the diaphragm is vibrated back and forth, causing the lever arm 4 tooscillate correspondingly. The microphones 2 and 3 mounted on the lever arm will tend to move with the lever arm, and the degree of movement of the microphones will be determinedby the rate of vibration of the lever: arm the body portions of the and the weight of microphones. If the lever arm vibrate slowly the microphones will move substanas much as the lever arm. On the tially other hand, if the lever arm vibrate at a relatively high frequency the weights 16 and 17 attached to the microphones will prevent them from following the movement of the le ver arm, whereb the diaphragms of the microphones will e flexed back and forth so as to vary the current flowing through the microphones. By changing the size of the weights 16 and 17, the relative movement between the body portions and dlaphragms of .the microphones can be regulated so as to regulate the range of sounds through which the microphones will be. appreciably responsive.

Another factor determining the relative movement between the body portions of the microphones and the diaphragms of the microphones is the stifiness of the latter. If the diaphragms be relatively heavy and stiff, the body portions of the microphones will follow the diaphragms at higher frequencies than if the diaphragms be relatively thin and flexible.

Fig. 2 illustrates the fact that the micr0- phone may be mounted directly on the sound-responsive diaphragm instead of upon the pivoted lever. However, the lever support is preferable for most purposes, inasmuch as it relieves the sound-responsive diaphragms from the weight of the microphones without adding appreciably to the resistance to the movement of the micro phone diaphragms. 'lhe lever arm also makes it possible to acutate any desired number of microphones from a single soundresponsive device. By disposing the microphones equidistantly from the pivot point the microphones are equally efiected.

In Fig. 1 only two microphones are associated with the diaphragm 1, but any desired number, depending upon the length of the lever arm, could be employed as illustrated in Fig. 4. By virtue of the microphone being mounted on opposite ends of the lever arm they operate correspondingly. They may be connected either in parallel or series, and an audion or other amplifying device may be employed in conjunction therewith. Obviously the sound-responsive diaphragins may be utilized to receive sound impulses transmitted either through the air or through water. When employing the apparatus for submarine sound detection the diaphragms may be mounted in sound boxes in any suitable manner or they may comprise the shell of a ship; that is, the rodsfi and 22 may, if desired, be connected to the shell of the ship instead of to diaphragms.

' The operation of the structure shown in Fig. 3 is similar to that of Figs. 1 and 2, the air resistance of the disk serving to damp the vibration of the microphonei The piston 24 in Fig. 2 and disk 33 in Fig. 3 each constitutes a damping v ne, the chief difference bination, a

betweemthe two being-"thatsthe former moves in a closed? space whereasrthe latter moves inthe'opom While I'preferably connect the diaphragm of the microphone cell. with the sound-responsive device it is to be understood that when. employing dragging means as abovedescribed the-parts maybe-reversed That is, the carbon cup may be connected-"to the sound-responsive diaphragm and the damping or dragging means may be connected to the diaphragmof the microphone-cell.

From the foregoing'it will be evident that my improvd apparatus is peculiarly-adapted toreceive sound waves throughout' a certain range of: frequencies and at the same time to besubstantially unresponsive to sound dis turbances which: are not included within the predetermined range. Thus I may re ceive comparatively i'feehle signalswithin the limited: range of frequencies from'a distance notwithstanding the concomitant occurrence of loud noises outside the limited: rangeeither' at short on long distances. And inasmuch as most interferingnoises are of relatively low frequencies my apparatus is comparatively free from disturbances, whereas fixed back microphones are subject to great. liability of injury from loud noises nearby- B utilizing the principle of inertia together with a damping or dragging eflect accord. ingto the present-invention signals or sounds of certain character may be receivedfrom variable distances-throughout a wide range of intensities without substantial liability of injury or disturbance to the microphones.

I claim:-

1. In a sound detecting apparatus, a sound receiver, a microphone comprising a cell provided with a diaphragm, cooperative electrodes mounted upon the cell wall and diaphragm respectively, means connecting the diaphragm directly to said sound: receiver, means supporting said cellfor movement with said receiver, and -means for damping the movement of said cell so that when said sound receiver moves slowly both of said electrodes are moved slowly with the sound receiver but with substantially no relative movement therebetween, and when the sound receiver moves rapidly the electrode carried by the diaphragm is move relatively to the other electrode, said other electrode being restrained from movement said damping means.

2. In a sound detecting apparatus in com- "sound receiver, a microphone comprising a cell having a flexible diaphragm, electrodes within the cell, one of said electrodes being carried by the cell walland another by the diaphragm, means con-- necting the diaphragm directly to. the sound receiver, means supporting said cell for bodily movement with said sound receiver, and

I said sound iguana a! damping vane connected: tosaid cell for opposing movement thereof', so that when sa1d"sound"reoeivor moves slowly both on said/electrodes are moved slowly: with the soundr'ecoiver 'but' without substantial rcla tive movement therebetween and when the soundreceiver moves-rapidly the diaphragmsupportedelectrode is moved relatively to theotherelectrode, movement of the latter being opposed by said damping vane. A

3. Sound detecting apparatus comprisingsound receiver, a microphone having two electrodes movable relatively: to each other, means connecting one ofsaid electrodes to receiver so as-to move with the receiver, the other electrode'being connected to the sound receiverthrough the first electrode, and supporting means for the microphone independent of: said sound receiver and constructed and arranged topermit movement of: said microphone in consonancc with the sound' receiver.

4. Sound detectingapparatus comprising a sound; receiver, a microphonic cellhaving two electrodes movable relatively to each other, means connecting one of said electrodes to said sound receiver so as to move with the receiver, the other electrode being connected to the sound receiver through the first electrode, and a pivoted arm supportingthe cell so that it can move with the sound receiver.

5. Sound detecting apparatus comprising a sound receiver, a plurality of microphonic cells each having two electrodes movable relatively to each other, and a pivoted arm connecting one electrode of each cell to thesound receiver, the other electrode of each cell being connected to the sound receiver through. the first electrode, whereby when said arm is moved slowly by said sound receiver said cells are moved bodily without substantially any relative movement between the electro es thereof and when said arm is moved rapidly said first electrodes are moved: relatively to said second electrodes.

6. Sound detectlngaparatus comprising a sound receiver, a pivoted arm connected to said sound receiver, and a plurality of microphonic cells supported upon said arm through the medium of their diaphragms.

7 Sound detecting apparatus comprising 6. a sound receiver, a pivoted arm connected I and a plurality of to said sound receiver, microphonic cells supported upon said arm through the medium of their diaphragms equidistantly from the pivot of the arm.

8. Sound detecting apparatus comprising a sound receiver, a pivoted arm connected to said sound receiver, and a plurality of microphonic cells mounted on said arm through the medium of their diaphragms equidistantly from the pivot of the arm and on opposite sides thereof. 9.

sound detecting device comprising 1,417,786 a a pivoted lever arm provided with a supdiaphragm, the cells and diaphragmsof'the port extending substantially at right angles series being arranged in alternation, and 10 to its longitudinal axis, and a plurality of means connected to the several diaphragms similarly disposed microphones mounted in whereby to support said microphones upon 5 spaced relation upon said support. the lever arm. a

10. A device of the class described having Signed by me at Boston, Massachusetts, an oscillating lever arm, a series of 'microthis twenty-ninth dag of October, 1917. phone devices each comprising a cell and a M L. WALKER. 

